Certain freely floating wave energy types of wave energy converters have been disclosed by the present applicant's previous patent applications and granted patents, namely the “Free Floating A Wave Energy Converter” under Indian Patent Number 239882, “Free Floating Wave Energy Converter” (FFWEC)/(US Patent # US20080229745), etc., “An Improved Free Floating Wave Energy Converter” (IFFWEC)/[Indian Application 2511/CHE/3458], WO 2013014682 A2), PCT/1N2012/000510, EP20120753590, CA2844023A1, CN103814211A, US20140157767], and as well the US application titled, “Free Floating Wave Energy Converter With Control Devices”.
The above quoted inventions essentially consist of Inlet and flexible pipe, floating on a body of water, i.e. ocean surface and adapting to wave form. The mouth of the flexible pipe is in fluid communication with an inlet and its outlet in further fluid communication with power takeoff and other devices. The inlet doses air-water slugs into the flexible pipe, which get pushed forward by transverse waves, progressively building up pressure in it—which could be used to drive conventional Hydro-generators or pump water for any other purpose.
The present invention discloses certain improvements for enhancing and controlling buoyancy of WECs employing flexible pipes to extract wave energy.
In the prior art, an Indian Application No. 2511/CHE/2011, describes the use of inflatable tubes 1300, 1302, wherein FIG. 13B shows an embodiment having certain means and methods for preventing the flexible pipe from sagging or sinking in a body of water.
The arrangement was also meant to let a segment of the flexible pipe 204 to go below a wave trough, up to a controlled depth, thereby increasing the amplitude or the effective wave height of the flexible pipe 204, as compared with the wave height of the body of water. Consequently, the wave energy absorption capacity of the flexible pipe 204 would increase, proportional with the effective wave height. To expose the flexible pipe to a larger wave front, the flexible pipe could be oriented at an angle to the oncoming waves.
Reference is also made to FIG. 1 of the India Patent Application 2511/CHE/2011 and the corresponding explanation therein, in which the pressure head created by the flexible pipe 204 is shown as the sum total of the effective wave heights, less frictional and other losses.
However, it would be apparent to one skilled in the art that, to create a pressure head in actual conditions, several other factors would also be involved, such as the force required for pushing the water slugs forward, at certain velocity, friction and rate of discharge against a pressure head. In addition to these forces there will also be certain frictional losses, when the flexible pipe goes below water surface, due to water friction on the exterior surface of the flexible pipe.
As such, the effective width or capture width of the air segment of flexible pipe 204 and inflatable tube 1300 1302 might not be sufficient to prevent the arrangement from sagging or sinking below wave crests, particularly when the pressure differential (effective wave height) is increased.
Furthermore, details of attaching the inflatable tubes 1300 1302 to the flexible pipe 204 and the added advantages that would accrue from the arrangement were not discussed in the previous invention application.
The present invention discloses details of an embodiment having certain improvements, additional features and advantages.